Keith Hollis

Keith Hollis

Associate Professor

Research Interests

The Hollis Group designs and develops next-generation organometallic ligands and complexes for many applications, which often requires the development of new synthetic methodologies. Access to new molecules and materials is required to solve many of the technological challenges facing society, such as improving energy-efficiency, direct conversion of solar energy to useful forms, and more cost-effective access to medicines. These goals are reached by developing efficient, scalable syntheses of molecules with interesting properties.

Basic Synthetic Methodology Development

A few years ago, the Hollis Group developed the seminal methodologies that allow access to a new class of organometallic pincer complexes – CCC-NHC ligands, which contain two donor N-heterocyclic carbenes (NHCs) with no spacer between the central aryl donor and the NHC donors. The core of the synthesis starts with a Cu catalyzed aryl amination that we routinely perform on the 120 g scale. It is followed by an alkylation by simple nucleophilic substitution.

Cu Catalyzed Core Synthesis –

This metalation/transmetalation strategy has proven highly successful as the Hollis group has now prepared examples from almost every group in the transition metal series.

The societal challenges that 21st century science is addressing require fundamental advances – the development of technologies that currently are not in existence. To sustain any kind of technologically-advanced society (energy-driven society) beyond the lifetime of our great-grandchildren major scientific-breakthroughs are required. At present, “No economic activity is yet sustainable…” [Duma12]. Many different avenues require exploration and, eventually, exploitation in full-scale economic application to bridge the time between the current state of the world and a carbon-neutral, fully-renewable energy economy. Reaching such a goal will solve many of the challenges we face, world-wide, that are driven by competition for limited resources. While a multi-pronged approach to a sustainable future is required with emphases in many areas, we are focused on developing, fully characterizing and engineering materials for improving photovoltaic (PV) efficiency, an approach to utilizing our greatest source of renewable energy (solar energy capture). Much fundamentally new science must be developed. The CCC-NHC Pt complexes depicted below absorb UV light and emit blue, a much needed color for OLEDs, and are phtostable for extended periods of time.

The ability to fix (convert to usable, high-value chemicals) nitrogen (N2) and carbon dioxide (CO2) are critically important chemical research frontiers. Converting nitrogen to ammonia for fertilizer is crucial for feeding the world. We must be able to efficiently sequester (chemically capture) CO2 emissions in power generation to fuel a technologically-advanced, energy-driven society while averting the looming global warming situation. The development of high energy organometallic complexes capable of these feats is an area of rapidly expanding research. Access to low valent versions of materials with the CCC-NHC ligand architecture are predicted to be robust and capable these conversions. Similar chemical reactivity parameters are required to convert unactivated C-H bonds into useful starting materials for the chemical industries.

The development of more efficient, catalytic methodologies for preparing organic compounds leads to more cost-effective synthetic procedures for the preparation of pharmaceutically-active compounds for the treatment of human disease thereby alleviating human suffering. Complexes prepared for the first time in the Hollis research group have been demonstrated to be effective for the formation of C-N bonds (hydroamination), C-Si (hydrosilylation), C-C (Michael addition) and C-B bonds (Michael addition).